Pulp logs are generally transported to a wood yard located at a paper mill, lumber mill or the like aboard a vertical stake logging truck. Typically, the truck arrives at the wood yard carrying a load of logs which have been precut to a predetermined length such as four or eight feet and which have been arranged in a plurality of tiers along the length of the truck, with each tier weighing several tons depending upon the dimensions of the logs and the type of wood. Prior to the loading of each tier of logs onto the truck, a cable pulp sling is typically centered transversely thereunder with each end of the pulp sling being manually secured to a fastening element located on the upper section of an appropriate truck stake, in a position which cannot be accessed by workmen standing on the ground. Consequently, at least one workman is required to climb up on top of the logs, which are commonly wet, frozen and/or covered with ice, in order to secure the ends of each cable pulp sling to the corresponding fastening elements, thereby increasing the probability of accidental injury or death due to falls, slips, shifting logs or other hazards associated with the log loading process.
After arriving at the wood yard, each of the log tiers on the truck is unloaded by manually securing the ends of the associated pulp sling to a slip-hook arrangement located at the end of a crane operated hoisting cable. As the hoisting cable is raised upwards by the crane, the slip-hook arrangement tightens the attached pulp sling around the tier of logs, thereby enabling the tier to be lifted out of the truck and transferred to the appropriate location in the wood yard. Again, because of the inaccessible location of the ends of the cable pulp slings, at least one workman must climb up on top of each tier of logs to attach the corresponding pulp sling to the slip-hook arrangement. Depending upon the number of log tiers carried by the truck, a workman may be required to climb on and off the truck several times, thereby exacerbating the probability of accidental injury or death.
Workmen on the ground may also be injured while the log tiers are being unloaded from a truck and during the transfer of the unloaded logs t the appropriate section of the wood yard because of the inherent instability afforded by currently available crane operated log unloading systems. In particular, if a pulp sling has not been correctly centered under a tier of logs during the loading process, the logs may not be correctly balanced within the slip-hook arrangement and may not remain in a substantially horizontal orientation relative to the ground during the unloading process. Consequently, one or more logs may shift out of position, slide out from within the slip-hook arrangement and fall to the ground crushing any workmen or equipment unfortunate enough to be located thereunder.